John Donne speaks this poem himself. Now, that's a bold and potentially risky statement. It's often a fatal trap to confuse a poem's speaker with the poet his/herself. In this case, though, we have history and biography to help us out. We know, for example, that he was leaving to go to continental Europe and his wife was to remain in England. And we can just imagine him reading the poem to his wife right before he boards the ship.
This speaker also has Donne's characteristic wit and flair for argumentation, but it's a more mature voice. This isn't some pick-up line, some logical reason why some girl should throw herself at him (seriously, read "The Flea" for a slightly… different approach). This is isn't just a lawyer writing a poem to impress his friends—this is a man speaking to his wife.
There's one notable shift in this poem as a result of his audience. Many of Donne's love poems are cocky and hypothetical, written as if by some semi-sleazy guy trying to pick up just another chick. They often have crazy endings that are intended to be a little shocking or outrageous, almost like the punch line to a joke. But, because this is personal—this is really the poet speaking here—the poem ends on a sweet, quiet note. We think Mrs. Donne appreciated that, don't you?